The invention relates to a device for positioning at least one optical component inside an endoscopic system.
Within the meaning of the present invention, optical components are to be understood as, for example, lenses, filters, diaphragms, polarizers and the like, which can be used in an endoscope optic. Without restricting the generality of the invention, an optical component can also include a structural group made up of the aforementioned elements.
Within the meaning of the present invention, an endoscopic system can, for example, be an endoscope into which the device mentioned at the outset is integrated.
The beam path of the endoscopic system propagating along the optical axis can be the beam path of illuminating light propagating from proximal to distal and/or the beam path of observation light propagating from distal to proximal.
A particular application of the present invention is the use of a device mentioned at the outset in an endoscope for photodynamic diagnosis, for photodynamic therapy, or for diagnosis by fluorescence. In this particular application, the at least one optical component is normally a color filter to permit high-contrast observation of the tissue to be examined, free from the background radiation which is caused by the exciting light superposed on the observation light and which interferes with viewing. In addition, in this particular application of the device mentioned at the outset, conventional viewing of the tissue area with white light is also desired, so that such color filters not only need to be able to be brought easily into the beam path but also once again removed from it.
A device known from DE 197 13 276 A1 and used for positioning components inside endoscopic systems has, in one illustrative embodiment, a revolving wheel which rotates in the housing of the device about the longitudinal centre axis of the housing. The revolving wheel carries three optical components distributed in one plane, these optical components being able to be pivoted into and back out from the beam path of the endoscopic system about the longitudinal axis of the housing as the pivot axis. The longitudinal axis of the housing extends parallel to the optical axis but is a distance apart from it. This is disadvantageous, however, particularly in an endoscope, since the optical axis of an endoscope coincides with the longitudinal centre axis of the sometimes thin shaft of the endoscope. In the known device, this means that the housing of the device cannot be arranged concentric to or symmetrical with the longitudinal axis of the shaft, but rather extends beyond the shaft farther on one side than on the opposite side.
If one were to modify this known arrangement such that the housing of the device surrounds the optical axis of the endoscopic system concentrically or symmetrically, and assuming an unchanged diameter of the revolving wheel which cannot be made smaller because of the predetermined size of the optical components, the housing would have to be increased in diameter by about 1½ times, which would result in the disadvantage of a device taking up considerable space transversely with respect to the longitudinal axis.
Because the carrier is designed as a revolving wheel, the distance of a respective midpoint of the optical components to the pivot axis is relatively small, with the resulting disadvantage that the displacement of an adjustment member by the user of the device for pivoting the respective component into and back out from the beam path is very considerable. This disadvantage is heightened further by the fact that the distance of a driven element, provided on the revolving wheel, to the pivot axis is relatively large, since this distance cannot fall below a certain minimum amount, because otherwise the material bridge of the revolving wheel between two adjacent components is too narrow. Thus, the adjustment member has to travel a relatively great distance in order to switch the revolving wheel from one state to the next, which is an impediment to rapid and comfortable switching of the device.
In order to remedy this disadvantage, it has been proposed in DE 199 03 437 A1 to arrange the at least one optical component on an L-shaped carrier which is pivotable about a pivot axis extending transversely with respect to the longitudinal axis of the housing and thus transversely with respect to the optical axis of the endoscopic system. With this design of the device, it is possible to achieve, compared to the aforementioned known device, a housing with a smaller dimension transversely with respect to the longitudinal axis of the housing. In this known device, however, another disadvantage arises. For the at least one component pivotable into and out of the beam path, a gap corresponding to the thickness of the optical component is usually provided, extending in the direction of the longitudinal axis. In the axial direction, this gap is often bounded by other components of the endoscopic system, for example imaging lenses or diaphragms. In the direction of the optical axis, the gap for the component which is to be pivoted inward and outward should as far as possible be only slightly greater than the axial dimension of this component. However, because of the pivotability of the at least one component about a pivot axis extending transversely with respect to the optical axis and because of the associated range of pivoting, the at least one component requires a gap width in the axial direction which considerably exceeds the axial dimension of the component. The disadvantage of this known device thus lies in a structural restriction of the optical system as a result of the considerable range of pivoting of the component.